Technical News

Exclusively for Allan Block Design Professionals

June 2023

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Our Design Professional ABU Online events were created to help you with your retaining wall needs. Our local production and sales partners will be happy to schedule in person training on any topics you see below (call us if you are looking for those individuals) but feel free to use these to help with immediate needs.

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Inspiring Project Ideas








In this Issue:

Case Study: Simplify Rural Creek Crossings with GRS - IBS

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Midland is a community located about two hours north of Detroit, MI. The surrounding area is vastly different from the larger Detroit metro. Filled with streams and creeks, access roads and bridges are critical to connect the rural parts of the community with the town. So, when maintenance is required, the project needs to be executed with speed and efficiency to minimize the disruption to the local community. A geosynthetic reinforced soil with integrated bridge system (GRS-IBS) design was being considered, but the concrete masonry units (CMU) typically used in these applications were not aesthetically pleasing. Sam Jansen with Consumers Concrete Corporation was able to propose an Allan Block alternative that could be used in place of the drab CMUs.


With the help of the Allan Block engineering team and the local design professional, Allan Block was approved. Consumers Concrete was able to host an AB Contractor Certification Workshop and train the Midland County Road Commission's crew. Now it was time to get to work. Even though this was the first GRS-IBS installation in the county, the crew on the job was able to complete their work in a couple weeks.

GRS- IBS _Nails

Typically, segmental retaining walls are built on a base of compacted stone, but the engineering firm, OHM Advisors, chose to build on a concrete foundation that used a tongue and groove connection. The choice was made so they didn't have to divert the creek and improved construction time for the abutments. Art Buck with the Midland County Road Commission even commented, "We put these projects off for years, but this ended up being a very smooth project." We look forward to seeing more of these small span solutions in the years to come from our friends in Midland County.

Check out the full case study* in our entire case study library.

Engineer Talk: Global Stability?

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What is Global Stability? It is defined as the rotation of the entire soil mass, which plays a role in retaining wall design. No matter how good the design and installation of a retaining wall is, if the soil mass rotates, the wall will move with it.

What are some conditions to look for that indicate Global Stability should be analyzed?

  • Slopes above and below a wall
  • Terraced structures
  • Tall walls
  • Poor soils
  • High ground water

Global Stability

After the global stability analysis is generated and the stability safety factors is less than satisfactory there are a few adjustments to the wall design that could boost the stability following our Best Practices approach.

Global Stability Best Practices

Ways to increase global stability:

  • Disrupt the failing slip surface by
    • increase grid length
    • increase wall embedment
    • add more layers of grid to distribute the load
  • Strengthen grid type
  • Increase infill soil friction angle
  • Foundation improvements below the wall

Although AB Walls will not do a full global analysis the following features are built in to help identify and tackle global stability problems.

  1. AB Walls creates a file that may be exported to RESSA to simplify the process of entering the wall configuration and therefore reduced the work to conduct the global review.
  2. By conducting an Internal Compound Stability review in AB Walls you can identify when the main point of entry for the majority of the slip arcs begin at the back of the 2H envelope this is an indicator that a global stability analysis is required.
  3. With the Limit Equilibrium portion of AB Walls we are providing the first step to a full global analysis.

For more information on Global Stability, check out our past webinars located on our Designer Resource Page or reach out to our engineering department at 800-899-5309 x 3.

Tools: AB Walls Exports to ReSSA for Global Stability

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At Allan Block, we pride ourselves on being able to provide a product that gives customers more usable land. However, not all reclaimed land is the same. You may have situations where slopes are at the top and bottom of the wall, poor site soils, and groundwater present; even a combination of conditions that could impact the overall stability. Internal Compound Stability (ICS), a feature included within AB Walls, performs a modified Bishop's slip arc analysis looking at an envelope 2x the height of the wall back from the wall facing. This analysis should not be used as a replacement for a true global stability analysis, but Allan Block has a solution by working with ReSSA, the industry leading global stability analysis program.


There are several software applications commercially available for performing global stability analysis calculations. Although the AB Walls Design Software does not perform global stability analysis, the software does allow designers to export cross sections directly into the ReSSA global stability analysis program. With a few simple clicks, designers can quickly create a file for any of their designed cross sections. This saves designers hours of time modeling their design in a global stability software application. The designer can then use ReSSA to run the analysis to ensure their design will not be impacted by slip arcs running underneath the wall or outside the wall envelope.

If you have questions on a project or need assistance to run the global stability analysis, feel free to reach out to our engineering department at or call 800-899-5309.

Contractor Talk: Economics of GRS-IBS Solution for Allan Block Segmental Retaining Walls

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The construction industry continually seeks innovative solutions that combine functionality, durability, and cost-effectiveness. One such solution gaining popularity in the realm of retaining walls is the Geosynthetic Reinforced Soil (GRS) with Integrated Bridge System (IBS).

The Federal Highway Administration (FHWA) estimates there are over 600,000 bridges across the U.S that need replacement. Of those, 70% could utilize GRS-IBS technology.


A couple of the advantages that can be seen from using GRS-IBS are:

  • Cost-Effective Construction: The GRS-IBS technique offers several cost-saving advantages over traditional retaining wall methods. By using granular backfill instead of large quantities of expensive concrete, the material costs are significantly reduced. Additionally, the use of precast concrete blocks simplifies installation, reducing labor costs and construction time. The FHWA states that GRS-IBS solutions typically save 25 to 60% in cost compared to a standard DOT bridge, and the system requires less or simpler life-cycle maintenance.
  • Improved Performance and Durability: The integration of geosynthetic reinforcement in GRS-IBS walls enhances their load-bearing capacity and stability. These walls can withstand a variety of soil conditions, including challenging terrains with high water tables or poor soil quality. The durability of Allan Block segmental retaining walls further contributes to long-term cost savings by reducing maintenance and repair expenses.

As the demand for sustainable and cost-efficient construction practices continues to grow, the GRS-IBS solution with Allan Block segmental retaining walls is poised to play a significant role in the future of retaining wall construction.

Have more questions about GRS-IBS? Watch our "GRS-IBS, What is it?" or give us a call at 800-899-5309 ext. 3 and talk to one of our experienced engineering staff members.


Hot Topic: Corners in Retaining Walls

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There are going to be sites where corners are going to be required in the retaining wall. We wanted to cover design considerations when your next project needs corners.

Design Considerations: When designing your wall projects in AB Walls Design Software it's important to identify where along your wall the corners will be. This is where you should identify cross sections so you can design your grid layout appropriately. Place a cross section directly at the corner so that the grid can be alternated. For example, the grids may be entering the corner on the odd course, but will move up one course to leave the corner on the even course.


Block Considerations: Allan Block has a 90-degree corner block that has texture on two sides. This simplifies the installation and minimizes the need for the contractor to miter cut blocks. Using the corner block will prevent a vertical seam at the corner and keep the structural integrity.


Inside corners do not require a special block, but the installers will need to modify the block to remove the front lip on the portion of the block that extends into the corner. This is something we cover in our Installation manuals and during our AB Contractor Certification classes.

Geogrid Considerations: The type and orientation of the geogrid reinforcement is important. Placement and usage of geogrid is vital with SRW corner design to ensure your wall project is stable. Inside corners require extending the grid past the wall 25% of completed height of the wall. On the next course alternate the direction of the grid that is extended.


For Outside corner grid applications, you will need to reinforce each side of the wall independently from each other. This means the grid should be installed with its strong direction perpendicular to the face in one direction, the alternating the grid direction on the next course as the wall is constructed.


As an engineer it is pertinent you keep these considerations in mind when planning and designing walls with corners. Contact us at if you need preliminary design assistance with corners or give us a call at 800-899-5309 at ex. 3.

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